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Impacts of Coral Growth on Geochemistry: Lessons From the Galápagos Islands
Paleoceanography and Paleoclimatology ( IF 3.2 ) Pub Date : 2021-03-12 , DOI: 10.1029/2020pa004051
E. V. Reed 1 , D. M. Thompson 1 , J. E. Cole 2 , J. M. Lough 3, 4 , N. E. Cantin 3 , A. H. Cheung 5 , Alexander Tudhope 6 , Lael Vetter 1 , Gloria Jimenez 7 , R. Lawrence Edwards 8
Affiliation  

Coral geochemical climate reconstructions can extend our knowledge of global climate variability and trends over time scales longer than those of instrumental data. However, such reconstructions can be biased by coral growth and skeletal architecture, such as growth troughs, off‐axis corallite orientation, and changing growth direction. This study quantifies the impact of skeletal architecture and growth on geochemistry using measurements of coral skeletal density, extension rate, and calcification rate, and uses these metrics to improve paleoclimate reconstructions. We present paired geochemistry‐density records at Wolf Island, Galápagos, from three Porites lobata corals: two new paired density and geochemistry records from one fossil coral, and new density data from two previously published modern geochemistry records. We categorize each sampling transect used in this record by the quality of its orientation with respect to skeletal architecture. We observe relationships between geochemistry and density that are not detected using extension or calcification rate alone. These density‐geochemistry relationships likely reflect both the response of coral growth to environmental conditions and the nonclimatic impact of skeletal architecture on geochemistry in suboptimal sampling transects. Correlations of density with Sr/Ca, Ba/Ca, and Mg/Ca are consistent with the Rayleigh fractionation model of trace element incorporation into coral skeletons. Removing transects with suboptimal skeletal architecture increases mean reconstructed SST closer to instrumental mean SST, and lowers errors of reconstruction by up to 20%. These results demonstrate the usefulness of coral density data for assessing skeletal architecture and growth when generating coral paleoclimate records.

中文翻译:

珊瑚生长对地球化学的影响:加拉帕戈斯群岛的教训

与仪器数据相比,珊瑚地球化学气候重建可以在更长的时间范围内扩展我们对全球气候变化和趋势的认识。但是,这种重建可能会因珊瑚生长和骨骼结构(如生长槽,离轴珊瑚岩方向和变化的生长方向)而产生偏差。这项研究通过测量珊瑚骨骼密度,扩张率和钙化率来量化骨骼结构和生长对地球化学的影响,并使用这些指标来改善古气候重建。我们提供了加拉帕戈斯狼岛的三种地球化学成对密度记录,该记录来自三份Porites lobata珊瑚:来自一个化石珊瑚的两个新的成对密度和地球化学记录,以及来自两个先前发布的现代地球化学记录的新密度数据。我们根据记录相对于骨骼结构的定位质量,对本记录中使用的每个采样样带进行分类。我们观察到单独使用延伸率或钙化率无法检测到的地球化学与密度之间的关系。这些密度-地球化学关系很可能既反映了珊瑚生长对环境条件的响应,又反映了次佳采样样面中骨骼结构对地球化学的非气候影响。密度与Sr / Ca,Ba / Ca和Mg / Ca的相关性与将痕量元素掺入珊瑚骨骼的瑞利分馏模型一致。去除次最佳骨骼结构的样点会增加平均重建SST,使其更接近仪器平均SST,并将重建误差降低多达20%。这些结果表明,在生成珊瑚古气候记录时,珊瑚密度数据可用于评估骨骼结构和生长。
更新日期:2021-04-08
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